To me "No True Scotsman" is a good argument only when the arguer does something about the maniacs who make zir look bad (and or help the person wronged).
If a nice normal guy is miffed by slimy misogynists, he should tell said misogynists to "shove it".
While the cartoon only illustrates the people who immediately jump on the "not all" bandwagon at the first hint that someone in a group they belong to might have done something wrong, I do think it's understandable for someone to get frustrated when people make sweeping, all-encompassing statements about said groups. I tell misogynists and racists to shove it constantly, but I can still sometimes get angry when someone makes a comment about how "all men are rapist pigs who think about nothing but sex" or "all white people are racist bigots who want to rule the world."